Chickens eating bedding?!?!?

To warm the coop for the winter we put straw in the coop and nesting boxes. I opened the coop for them (this is their first time on straw) and THEY WILL NOT STOP EATING IT! I heard that eating too much straw is dangerous. Is there any way you could prevent from eating? Will they get tired of it eventually? Is it even ok for them to eat such large amounts? PLEASE HELP!